The present invention is directed to low gauge, multi-layer films with skin layers that are extremely thin. In addition, the present invention is directed to such films laminated to other materials such as, for example, fibrous nonwoven webs.
The present invention is directed to extremely thin multi-layer films and their use with laminates. Such materials have a wide variety of uses, especially in the areas of limited use and disposable items.
Many products today require highly engineered components and yet, at the same time, these products are required to be limited use or disposable items. By limited use or disposable, it is meant that the product and/or component is used only a small number of times or possibly only once before being discarded. Examples of such products include, but are not limited to, surgical and health care related products such as surgical drapes and gowns, disposable work wear such as coveralls and lab coats and a personal care absorbent products such as diapers, training pants, incontinence garments, sanitary napkins, bandages, wipes and the like. All of these products can and do utilize as components, films and fibrous nonwoven webs. While both materials are often used interchangeably, films tend to have greater barrier properties, especially to liquids while fibrous nonwovens webs have, among other things, better tactile, comfort and aesthetic properties. When these materials are used in limited use and/or disposable products, the impetus for maximizing engineered properties while reducing cost is extremely high. To this end, it is often desirable to use either a film or a nonwoven to achieve the desired results because the combination often becomes more expensive. In the area of films, there have been previous attempts to make multi-layer films with reduced thicknesses. See, for example, U.S. Pat. No. 5,261,899 to Vischer wherein a three layer film is made with a central layer that comprises from about 30 to 70% of the total thickness of the multi-layer film. One advantage in forming multi-layer films is that specific properties can be designed into the film, and, by making the films multi-layer the more costly ingredients can be relegated to the outer layers where they are most likely to be needed.
It is an object of the present invention to provide a multilayer film which can be engineered to provide specific properties while providing such properties in a very thin gauge. Another object of the present invention is to combine such low gauge films with other support layers such as layers of fibrous nonwoven webs to increase strength and provide aesthetic properties. The means by which such objectives are achieved can be more fully comprehended by a review of the following specification, drawings and claims.
The present invention is directed to multilayer films and multilayer film/nonwoven laminates. The films are made by conventional film forming techniques such as cast and blown coextrusion film forming processes. The films are created with a core layer made from an extrudable thermoplastic polymer with the core layer defining a first exterior surface and a second exterior surface. In the most basic configuration, a first skin layer is attached, usually simultaneously due to the coextrusion process, to the first exterior surface of the core layer to form a multilayer film. The multilayer film defines an overall thickness with the first skin layer defining a first skin thickness which comprises less than about 10 percent of the overall thickness of the multilayer film. This is due to the stretching of the extruded film to such a degree so as to thin the multilayer film to within the dimensions defined herein. As a result, the thickness of the first skin layer will not exceed about 2 micrometers. Given the extremely thin nature of the multilayer film, it may be desirable to laminate the multilayer film to another material such as a support layer. Suitable support layers include, but are not limited to, such materials as other films, fibrous nonwoven webs, woven materials, scrims, netting and combinations of the foregoing.
In other embodiments of the present invention, the core layer may have a first skin layer attached to the first exterior surface of the core layer and a second skin layer attached to the second exterior surface of the core layer. In such situations, the first skin and the second skin layer should have a combined thickness which does not exceed about 15 percent of the overall thickness and more desirably where neither the first skin thickness nor the second skin thickness exceeds more than about 7.5 percent of the overall thickness of the multilayer film. If desired, one or more of the layers may contain other additives such as, for example, a particulate filler. Most typically, such fillers will be primarily utilized in the core layer in, for example, a weight percent of at least about 60 percent, based upon the total weight of that particular layer.
It is also possible to make multilayer films which are breathable either through the use of specialized polymers which permit diffusion of gases through the layers and/or through the use of particulate fillers. Normally, to make such films breathable, they are stretched and/or crushed between compression rollers so as create voids in and around the particles to permit the transmission of water vapor and other gases. Typically such breathable multilayer films will have water vapor transmission rates of at least 300 grams per square meter per 24 hours.
Such films and laminates have a wide variety of uses including, but not limited to, applications in personal care absorbent articles including diapers, training pants, sanitary napkins, incontinence devices, bandages and the like. These same films and laminates also may be used in items such as surgical drapes and gowns as well as various articles of clothing either as the entire article or simply as a component thereof.